1. Field of the Invention
The present invention relates to a caged roller bearing for use in, for example, a crankshaft support structure and a connecting rod support structure both employed in, for example, four wheeled vehicles, bicycles and multipurpose engines and also relates to a roller bearing assembly of a type utilizing the caged roller bearing and a cage for supporting a plurality of rollers. More specifically, the present invention relates to a technique of resolving a frictional wear and an excessive temperature rise, both of which will occur in the cage of the caged roller bearing.
2. Description of Related Art
The caged roller bearing is of a structure comprised of a plurality of rollers and a roller retaining cage, in which the outer peripheral surface of each of those rollers is held in linear contact with the raceway surface defined in each of inner and outer rings. Because of this structure, although the caged roller bearing has a small projected surface area to the bearing, it has advantages in high load bearing capacity and high rigidity. Accordingly, the caged roller bearing is largely employed in various fields of industries including, for example, automobile.
In general, for use with large and small ends of a bicycle, caged roller assemblies in the form of slide bearings or rolling bearings are employed. In the case of a two stroke combustion engine, the large and small ends are lubricated with a mist of a mixed liquid prepared by mixing a gasoline and an engine oil. Accordingly, since the slide bearing involves a frictional wear and an excessive temperature rise, roller bearings such as, for example, the caged roller bearing and a shelled radial bearing are generally utilized. It is, however, to be noted that the caged roller bearing, which is one of the rolling bearings used, has hitherto employed a copper plating or a silver plating in order to prevent an outer diameter and end faces of the roller retaining cage from being frictionally worn and/or being excessively heated.
At a high speed rotation which the copper plating or the silver plating cannot withstand against, the composite plating has been suggested, which has a base material comprised of nickel as a major element in which finely divided particles of fluorine resin are uniformly dispersed so as to represent an eutectoid structure (See the patent document 1 listed below.). The patent document 1 discloses a countermeasure for avoiding the excessive temperature rise and the frictional wear that may be brought about under the condition of high speed use.